Detachable terminal assembly for electrical lighting fixture



g- 9, 1955 A. 1. APPLETON 2,715,214

DETACHABLE TERMINAL ASSEM Y ELECTRICAL LIGHTING FI R Filed July 22, 19502 Sheets-Sheet l In uenfor Clrlhur I. Cgjfleton United States PatentDETACHABLE TERMINAL ASSEMBLY FOR ELECTRICAL LIGHTING FIXTURE Arthur I.Appleton, Northbrook, 111.

Application July 22, 1950, Serial No. 175,419

4 Claims. (Cl. 339-180) The present invention pertains to electricalfittings in general and more specifically to a novel detachable terminalassembly having particular, but by no means exclusive utility, inconnection with the overhead mounting of explosion-proof and vapor-prooflighting fixtures.

One object of the invention is to provide a terminal assembly of thecharacter set forth and which will permit a lighting fixture to bereadily attached to or detached from a supporting canopy by a simplemechanical operation performed entirely without regard to the electricalwiring.

Another object is to provide a detachable terminal assembly ofrelatively simple, inexpensive constructionand which will besufiiciently foolproof to preclude the possibility of shock or injury toeven the most unskilled servicer.

A further object is to provide a detachable terminal assembly which willbe particularly well suited for use with explosion-proof and vapor-prooftype fixtures where relamping and other maintenance operations normallyrequire the performance of several steps to disassemble the fixturewhile the servicer is positioned upon a high ladder or is working underother unfavorable conditions.

Other objects and advantages of the invention will become apparent asthe following detailed description proceeds, taken in the light of theaccompanying drawing wherein:

Figure 1 is an enlarged fragmentary vertical sectional view through anillustrative terminal assembly embodying the present invention.

Fig. 2 is a transverse sectional view through the assembly of Fig. l andtaken in the plane of the line 2--2.

Fig. 3 is an enlarged fragmentary vertical sectional view through one ofthe major components of the assembly shown in Fig. 1.

Fig. 4 is a perspective view detailing one of the flexible connectingelements of the assembly shown in Fig. 1.

Figs. 5 and 6 are transverse sectional views taken in oppositedirections along the plane of the line 55, 6-6 in Fig. 1.

Fig. 7 is an enlarged fragmentary vertical sectional view through amodified form of detachable terminal assembly also embodying the presentinvention.

While the invention is susceptible of various modifications andalternative constructions, certain preferred embodiments have been shownin the drawings and will be described below in considerable detail. Itshould be understood, however, that there is no intention to limit theinvention to the specific forms disclosed, but on the contrary, theintention is to cover all modifications and alternative constructionsfalling within the spirit and scope of the invention as expressed in theappended claims.

Referring more specifically to the drawings, there is shown in Fig. 1 anillustrative terminal assembly 10 embodying the present invention. Theassembly 10 'comprises a first terminal block 11 having contact means 12and a second terminal block 14 having contact means Patented Aug. 9,1955 ice 15 adapted for coaction with the contact means 12. Associatedwith the second terminal block 14 and dependably supported therefrom isa receptacle 16 for holding the base of a lamp 18 or the like. Theassembly 10 is housed within a fixed support, which in the presentinstance is a hollow fixture canopy 19, together with a detachablesupport which happens to be the casing 20 of a lighting fixture (shownfragmentarily in Fig. 1). The canopy 19 is of frusto-conical shape,being provided with a neck 21 for attachment to an appropriate overheadsupport and having a passage 22 for receiving suitable power supplywiring. The terminal blocks 11, 14, may be fixed to their respectivesupports in any suitable manner. Thus the block 11 is disposed inunderlying relation with a pair of lugs 24 integral with the canopy 19,being secured in place as by means of screws 25 threaded into the lugs24 and which engage keyhole slots 26 in the terminal block 11 (see Fig.2). The terminal block 14, on the other hand, happens to be providedwith peripheral threads 28 which engage corresponding threads 29 withinthe fixture casing 20. The block 14 in this instance seats against anannular shoulder 30 integral with the casing 20 and is locked in placeas by means of one or more set screws 31.

Provision is made for automatically disconnecting the contact means 15of the terminal block 14 from the contact means 12 of the terminal block11 as an incident to the simple mechanical step of detaching the fixturecasing 20 from the canopy 19. By the same token, provision is also madefor automatically connecting the foregoing electrical contact means asan incident to the step of attaching the casing 20 to the canopy 19. Forthis purpose, the contact means 12, 15, are bodily separable in onedirection and movable relative to each other in a plane transverse tothe direction of bodily separation.

In the illustrative assembly 10, the contact means of the terminal block11 comprises slip type contact elements in the form of resilient prongs32, 34, respectively attached to terminal elements 35, 36, the latterbeing adapted for permanent connection with the power supply wiring. Bythe same token, the contact means of the terminal block 14 comprisesupstanding contact elements in the form of a central pin 38 and asurrounding ring 39.

By reason of the structure thus far described, when the assembly 10 isin the condition indicated in Fig. l, the fixture casing 20 may readilybe detached from the canopy 19 simply by loosening set screw 40 andunscrewing the casing 20 from the threaded skirt of the canopy. Theterminal block 14, together with the central pin 38 and the surroundingring 39, rotates with the fixture casing 20 during such action, the pin38 pivoting relative to the resilient prong 32 of the terminal block 11and the ring 39 sliding relative to the prong 34 of the block 11. Thisrelative sliding and pivoting occurs in a plane transverse to therotational axis of bodily movement between the fixture casing 20 and thecanopy 19 as the casing 20 is attached to or detached from the canopy19.

Means is provided for protecting the person who services the assembly 19against electrical shock due to inadvertent contact with the live one ofthe terminal blocks upon separation of the same in the manner describedabove. This is accomplished by imparting a socalled dead frontcharacteristic to the live terminal block, the latter being the block 11attached to the canopy 19. In keeping with such purpose, the contactelements 32, 34 of the terminal block 11 are housed within recesses 41,42 formed in the inside face 44 of the terminal block. This face is, ofcourse, protectively enclosed within the canopy 19. Communicatingbetween respective ones of the recesses 41, 42, and the opposite face 45of the terminal block 11, are relatively narrow apertures 46, 48. Thelatter are adapted to receive telescopically the upstand- 7 material 68.

ing contact pin 38 and the surrounding contact ring 39 of the terminalblock 14. Preferably, each of the apertures 46, 48 has a cross sectiononly slightly larger than the corresponding one of the elements 38, 39which it receives. Consequently, when the casing and the terminal block14 are separated from the canopy 19 and the terminal block 11, it ispossible to bring ones hand into contact with the exposed face of theblock 11 without danger of receiving an electrical shock. Moreover, therelatively small cross sectional area of the apertures 46, 48 makes itextremely unlikely that a servicer will inadvertently bring a screwdriver or the like into contact with either or both of the live prongs32, 34.

For the purpose of protecting the receptacle 16 from vibration andshock, resort is had to common resilient supporting and'conductingmeans. Referring more particularly to Figs. 1, 3, and 4, it Will benoted that such means comprises resilient plate 49 of Phosphor bronze orthe like. The plate 49 is of generally annular shape and in thisinstance has two pairs of diametrically opposed holes 50, 51, each pairbeing located on a diameter perpendicular to that of the other. Theplate 49 is fixed mechanically to the terminal block 14 and connectedelectrically to the contact ring 39 as by means of rivets 52 andsurrounding bushings 54, the rivets 52 projecting through the holes 50.The plate 49 is fixed mechanically to the receptacle 16 and connectedelectrically to a socket fitting 55 within the same as by means ofscrews 56. The latter engage suitable threads formed in embossments 58surrounding the holes 51. Inter-posed between the terminal block 14 andcentral contact pin 38, on the one hand, and the receptacle 16 and acentral contact post 59, on the other hand, is a coil spring 60 whichserves as an appropriate electrical connecting link between the parts38, 59. The spring 60, of course, yieldably urges the parts 38, 59 inopposite directions.

Turning now to Fig. 7, there is shown another illustra tive detachableterminal assembly 10A of slightly modified form but'also embodying thepresent invention. The assembly 10A comprises a supporting canopy 19Agenerally similar to the canopy 19, together with a pair of terminalblocks 11A, 14A having contact elements 32A, 34A, 38A, 39A substantiallyidentical with those already described above. In the present instance,however, the terminal block 14A is made integral with receptacle 61which is rigidly fixed to removable member 62 of a lighting fixture asby means of screws 64 and annular shoulder 65. The receptacle 61 isgiven a vibration-proof characteristic by mounting its socket fitting 66in a manner closely similar to that used for mounting the receptacle 16of the assembly 10. In this case, however, the socket fitting 66 hasfixed to its inside end a block of insulating An annular resilientconductor plate 69 is mechanically and electrically interposed betweenthe contact ring 39A and terminal block 14A, on the one hand, and thesocket fitting 66 and insulating block 68, on the other hand. This isreadily accomplished as by means of rivets 70 and suitable connectingscrews (not shown) such as the screws 56. A loading spring 71 isinterposed between central contact pin 38A and central post 72 of thereceptacle 61. Since the action of the modified terminal assembly 10A issubstantially identical to' that of the assembly 10 upon installationand removal of the fixture member from the canopy 19A, further commentin that regard would appear to be unnecessary.

In the light of the foregoing description, it will be readilyappreciated by those skilled in the art that detachable terminalassemblies embodying the present invention possess a number of importantadvantages. First of all, such assemblies possess considerableversatility, being susceptible of mass productive manufacture instandardized sizes for use with a wide variety of light fixtures. Theperformance of relamping and other maintenance operations is greatlyfacilitated by the use of these assemblies since they permita servicerto detach. an entire fixture by a simple mechanical operation which caneasily be performed at the top of a ladder, and at the same time toreplace such fixture with a spare by an equally simple operation. Thereis no need for the servicer to concern himself with the disassembly ofnumerous small electrical and mechanical parts under diificult andhazardous con-.

'istic of the terminal block.

I claim as my invention:

1. A detachable terminal assembly for lighting fixtures, said assemblycomprising the combination of a supporting canopy, a first terminalblock fixed to said canopy and having an inside face enclosed by saidcanopy and an outside face exposed through the entrance to said canopy,said inside face having recesses therein, said first terminal block alsohaving relatively narrow concentric apertures therein communicatingbetween respective ones of said recesses and the outside face of saidblock, contact elements in the form of cantilever supported resilientarms located within said recesses but totally behind said apertures, asecond terminal block having means for mounting the same within alighting fixture detachably secured to said canopy, and coacting sliptype contact elements fixed to said second terminal block in concentricprojecting relation with each other, said coacting contact elementsbeing telescopically housed within said narrow apertures and disposed insubstantially perpendicular abutting relation with said resilient armswhen said terminal blocks are in assembled relation.

2. In a detachable terminal assembly for lighting fixtures, thecombination comprising a supporting canopy, a dead front terminal blockmounted on said canopy and having recesses in the inside'face thereof,said block having substantially concentric apertures of relatively smallcross section communicating between said recesses and the outside faceof said block, contact elements mounted in said recesses, means forconnecting said contact elements to a source of power supply viaconductors housed within said can py, a second terminal block, a supportfor said second terminal block having threads thereon, additionalupstanding concentric contact elements including means mounting the sameon said second terminal block in registry with said concentricapertures, and thread means on said canopy for guiding said additionalcontact elements into said concentric apertures to establish contactwith said first contact elements.

3. In a detachable terminal assembly for lighting fixtures, thecombination of a fixed terminal block having recesses in its insideface, said block also having a relatively small central aperture and arelatively narrow surrounding circular aperture underlying respectiveones of said recesses and communicating between the same and the outsideface of said block, resilient prong contact elements cantileversupported within said recesses but totally behind said outside face, amovable terminal block susceptible of both bodily and rotationalmovement along and about a common central axis relative to said fixedterminal block, a central contact pin and a surrounding contact ringmounted upon said movable terminal block, and means locating said pinand ring on said movable terminal block for abutting engagement insubstantially perpendicular relation with said resilient prong elementswhile telescoped Within respective ones of said central and surroundingcircular apertures.

4. In a detachable terminal assembly, the combination comprising a deadfront terminal block, a fixed cup-shaped support, means for mountingsaid block in said support with the inner face of the formersubstantially enclosed by the latter, yieldable resilient contact armsand means mounting the same in spaced relation on the inner face of saidblock, said block having relatively narrow concentric circular aperturestherein underlying respective ones of said contact arms, a secondterminal block having upstanding concentric circular contact elementsfixed thereto for substantially perpendicular abutting engagement withsaid contact arms when said elements are inserted through correspondingones of said apertures, a second support having means for detachablysecuring the same to said fixed support, and means for mounting saidsecond block on said second support to aline said 5 contact elements forinsertion through said apertures as an incident to attachment of the twosupports.

References Cited in the file of this patent UNITED STATES PATENTS1,982,781 Benjamin Dec. 4, 1934 1,987,464 Campbell Jan. 8, 19351,993,385 Saaf Mar. 5, 1935 2,003,948 Mess June 4, 1935 2,127,124 LitnerAug. 16, 1938 2,225,461 Reynolds Dec. 17, 1940 2,312,017 Ackerman Feb.23, 1943 2,431,895 Tornblom Dec. 2, 1947

